In order to produce fine polymer powders, a special and unconventional cryogenic grinding system was established using liquid nitrogen, where a jet-vortex mill was used as the grinding mill. The major feature of this grinding process is that heat generation during the grinding period was eliminated. The results suggest that this cryogenic grinding system may be suitable for studying the grinding properties of polymeric materials. It may also be helpful in understanding mechanochemistry, e.g., the t-P-T conditions for different mechanochemical processes under cryogenic conditions (where T is the temperature, and P the pressure of the gas mixture in the grinding chamber). In addition, an Elbow-jet classifier was attached to the jet-vortex mill so that fine, medium and coarse products of polymeric powders could be obtained simultaneously. Chitin, a type of renewable natural polymer, was ground in the system and XRD analysis of ground powders showed they displayed highly activated properties. Unlike a high-energy mechanical milling process, such as a vibratory (bead) mill which requires more milling time t, the final properties of the ground polymer in the cryogenic grinding system were highly dependent on the temperature in the chamber of the jet-vortex mill. The grinding results of chitin also showed that the minimum diameters of the ground polymer products are larger than several tens of micrometers (e.g., 75 mum). The developed method offers a new choice for the production of materials. polymer modification (e.g., degradation), and recycling of wasted rubber and plastic.